1. Field of the Invention
The present invention relates to shaped articles having an antimicrobial function and also excellent resistance to washing.
2. Description of the Background
A variety of bacterial and mildew adhere to the human body and/or textiles via various media and propagate there. Upon propagation, they irritate human skin, deteriorate textiles, and smell bad, for example. In particular, where textiles of synthetic fibers, which absorb only a minor amount of sweat, are put on the human body, bacterial will propagate on the skin or clothing to which the sweat adheres, and then cause putrefaction, generating an unpleasant smell. Since polyester and/or polyamide fibers are widely used for making various types of clothing such as uniforms, Japanese style clothing and sports wear, as well as bedding and interior textiles, it would be extremely desirable to be able to prepare polyester or polyamide fiber textiles which are clean and do not smell badly, and which are hence safe and comfortable to wear.
At one time, organic tin compounds or organic mercury compounds were applied to fibers in order to impart an antimicrobial function to the fiber. Unfortunately, the toxicity of such compounds prevented most of these compounds from ever being used.
In the after-processing of textiles, organosilicon quaternary ammonium salts, for example, have been used as antimicrobial and mildew-resistant agents with greater safety. For example, Japanese Patent Application Laid-Open No. 51874/1982 discloses a carpet having adsorbed thereon an organosilicon quaternary ammonium salt and a process for producing the same. However, while silicon-associated quaternary ammonium salts are reactive with cellulosic fibers, and hence the cellulose textiles treated with them exhibit a wash-resistant antimicrobial function, these salts do not bond firmly with synthetic fibers and synthetic textiles treated with the same exhibit only a temporary antimicrobial function.
It is known that compounds of silver, copper and zinc, for example, which when wet generate silver ions, copper ions and zinc ions, respectively, have an antimicrobial function. For example, aqueous silver nitrate solution has been widely used as an antiseptic solution or sterilizing solution. However, a solution-form agent is inconvenient to handle and has only limited use. Therefore, if an ion or a salt of silver. copper or zinc were incorporated in a polymer, the polymer mi9ht be expected to have little such drawbacks and might be expected to be used in a wide variety of fields. For example, a method is proposed in Japanese Patent Application Laid-Open No. 147220/1979 which entails mixing a compound of a metal such as silver, copper or zinc, for example, in a polymer, and then forming the polymer into fiber. Further, a method is proposed in Japanese Patent Application Laid-Open No. 133235/1984 in which solid zeolite particles ion-exchanged with silver ion or copper ion are incorporated into organic polymers These methods however have a number of associated problems. For example, a metal compound exerts too great an influence on polymers, thus limiting the end-use of the final products. Also, there occurs operation troubles in the fiber manufacturing process, such as frequent filament breakage at spinning, shortening of spinneret pack filter life due to clogging, and frequent filament breakage at drawing process rendering the obtained drawn yarn very fluffy. However, even when the above problems are not encountered, the simple incorporation of a metallic ion into a polymer can not produce a sufficient effect, since migration of the inside metal ion having an antimicrobial function to the surface of the fiber is too slow, thereby lowering the level of the antimicrobial function of the fiber.
In Japanese Patent Application No. 123474/1981, a method is proposed which entails adhering a complex containing a compound of copper, silver or zinc and casein, which has been insolubilized in water, onto the surface of fiber. The complex on the fiber is resistant to washing because it is insoluble in water. However, in order to insolubilize casein, formaldehyde must be used, and hence there is the disadvantage that textiles made of such fiber may release formaldehyde during use.
Thus, a need continues to exist for synthetic shaped articles having an antimicrobial function, which maintain the inherent characteristics of polymers employed and which also have excellent resistance to washing and wearing, and, in particular, whose antimicrobial and mildew-resistant function does not decrease even after washing with water or with warm water.